Advanced Optical Systems, Inc. (AOS) has developed and demonstrated the Cable Angle Measurement System, a low-cost, accurate system for measuring a helicopter’s load position and motion at the end of an external sling. By using a camera, an LED target, and custom electronics, the AOS system measures the load’s angle with better than 0.1° accuracy across a 150° field of view and with 0.1°/sec angle rate accuracy. AOS’s highly-successful Phase I produced a working lab prototype that met or exceeded the customer’s field of view, accuracy, and angle rate accuracy requirements. During Phase II we will install a prototype on a Blackhawk helicopter capable of providing cable angle and angle rate data at 50 Hz with very low and deterministic latency. Our Phase II cable angle measurement system allows direct slung load stabilization by providing feedback to a human pilot, flight computer, or dedicated automatic load stabilization system.